Cable operators have widely deployed high-speed data services on cable television systems. These data services allow subscriber-side devices, such as personal computers, to communicate over an ordinary cable TV network Hybrid Fiber Coax (HFC) cable. A Cable Modem Termination System (CMTS) connects the cable TV network to a data network, such as the Internet. The Data Over Cable Service Interface Specification (DOCSIS) is one of the cable modem standards used for transferring data over the cable TV network.
In a DOCSIS network, the data traffic is classified by specified fields in the data packet headers into service flows (also referred to as flows, sessions, etc. in non-DOCSIS networks). Each service flow is buffered as it is received by the CMTS and then the CMTS arbitrates release of packets between the buffers for downstream transmission. In the downstream direction, the physical transmission of packets is over physical Radio Frequency (RF) channels to the cable modems.
In the latest DOCSIS version, version 3.0, each service flow can be transmitted over a single one of the RF channels (non-bonded, also called narrowband), or distributed over a plurality of the RF channels (bonded, also called wideband). Consequently, an RF channel can be used to carry a plurality of narrowband transmissions and/or a plurality of portions of wideband transmissions.
Although the wideband transmission scheme as described in DOCSIS 3.0 provides numerous benefits, the use of this wideband transmission scheme with existing arbitration schemes can lead to anomalies. In particular, the mixture of narrowband and wideband transmissions on a same RF channel can cause RF channel bandwidth to be allocated amongst service flows in a way that appears arbitrary in view of DOCSIS priority values or other QoS metrics associated with the service flows. The disclosure that follows solves this and other problems.